Simulation and energy analysis of the ABE fermentation integrated with gas stripping

The production of acetone, n-butanol and ethanol (ABE) by fermentation has recently gained renewed attention to produce fuels and chemicals from renewable resources. The main problem associated with the ABE fermentation is the self-inhibition of the process due to butanol toxicity to the culture. The use of a separation method, which enables selective removal of toxic components from the fermentation broth, may contribute to improve the economics of such process. This work concerns the recovery of butanol from a batch fermenter, in which the ABE mixture is recovered from the broth by means of gas stripping. The aim of this work is to compare the performances of the integrated fermentation-gas stripping process with those of a conventional batch fermenter. For this purpose, both processes have been modeled and their energy requirements have been determined by means of an energy analysis. Results suggest that the continuous product removal from the fermenter allows to reduce the fermentation time by 50%. Therefore, the process productivity is almost double. At the same time, the total specific energy requirement for the integrated recovery process is almost three times greater than that of the traditional batch process. This is essentially due to the duty required at the condenser for products recovery from the gas stream, as a result of the low concentration of ABE in the recovered stream. Therefore, the application of an integrated recovery process allows to increase the process productivity, but at the expense of an increase in the whole process energy demand.